The subprocess amplitudes discussed in this section hold in any c.m.s. as well as in the limits
\(Q^2\rightarrow 0\)  and \(\hat{t}\rightarrow 0\) . The latter limit is the region of DVMP
where factorization of the leading-twist contribution has been shown to hold for large \(Q^2\)  [1]},
for instance in Ji's frame [2]}. In this frame in which skewness is non-zero, \(\hat{s}\)  and \(\hat{u}\) 
are related to \(Q^2\)  by
\(\hat{s}\,=\, \frac{x-\xi }{2\xi }\,Q^2\,, \qquad \hat{u}\,=\,-\frac{x+\xi }{2\xi }\, Q^2\,,\) 
